This invention relates generally to aircraft fuel tank structures, and more particularly to a secondary enclosure for an aircraft fuel tank configured to seal the tank against fuel vapor leakage into occupied aircraft compartments.
In the observance of appropriate safety precautions and design criteria for aircraft fuel tanks, fuel carried within an occupied compartment of the aircraft must be enclosed in two separate (inner and outer) fuel vapor-tight containers, and the space between the two containers must be continuously drained and ventilated during flight. Certain high wing aircraft, such as the C-17A, may have the center wing section within the fuselage configured to include an auxiliary fuel tank. In such instances, special safety precautions are taken in the structure of the aircraft to ensure that the center wing tank is designed to protect the aircraft occupants and cargo from contact with liquid fuel or fuel vapors. In this type of aircraft, it is desirable to enclose the entire wing box structure containing the center wing tank with a secondary enclosure separate from the tank structure itself.
Existing aircraft tank structures having means to prevent leakage of liquid or vapor fuel into occupied compartments comprise fuel-tight bladder cells within the wing tank structure. These structures not only are costly and add extra weight to the aircraft, but have been found to produce pockets of unuseable fuel, to reduce available fuel volume, and to limit inspection and maintenance.
The present invention provides a novel secondary fuel tank enclosure for an integral center wing tank structure wherein the tank is surrounded by a plurality of removable panels of fiberglass honeycomb forming a vapor-tight, removable enclosure. The novel structure of the present invention provides a reliable vapor-tight seal around the fuel tank adjacent fuselage compartments. In addition, it provides desirable thermal and acoustic insulation, is lightweight, corrosion resistant, and inexpensive, and allows use of the entire wing for tankage. Furthermore, the design facilitates inspection and maintenance of the enclosed fuel tank and aircraft structure. Means may be provided additionally to vent aircraft cabin air overboard through the enclosure to remove any fuel leakage from the enclosure.
It is therefore, an object of the present invention to provide a secondary enclosure for aircraft fuel tanks to prevent fuel leakage into occupied aircraft compartments.
It is a further object of the present invention to provide a removable secondary enclosure for aircraft fuel tanks.
These and other objects of the present invention will become apparent as the detailed description of a representative embodiment thereof proceeds.